SILVER SPRING, MD. – A Food and Drug Administration advisory panel gave its unanimous support Nov. 14 to an H5N1 influenza vaccine designated for a national stockpile, where it would be reserved for use during an avian influenza pandemic or outbreak.
The FDA’s Vaccines and Related Biological Products Advisory Committee voted 14-0 that the influenza A (H5N1) Virus Monovalent Vaccine should be approved based on the safety and immune responses to the vaccine in clinical studies,
GlaxoSmithKline contracted with the U.S. government to develop the vaccine, which contains an antigen-sparing adjuvant that boosts the immune response. If licensed, it will be deposited in the U.S. Strategic National Stockpile and owned by the U.S. government, which would control the distribution and use of the vaccine in the case of a pandemic. GSK has no plans to market the vaccine,
The advisory committee agreed that immunogenicity and safety data on the "Q-Pan H5N1" vaccine support licensure for use in adults at increased risk of exposure or during a pandemic. The proposed indication is for the "active immunization for the prevention of disease in persons 18 years of age and older at increased risk of exposure to the influenza A virus H5N1 subtype contained in the vaccine." The vaccine is administered in two doses about 21 days apart.
Mortality from the infection is highest among children and young adults. GSK is conducting studies in children aged 17 months and older, with plans to expand the approval.
The influenza A (H5N1) virus is highly pathogenic, contagious, and deadly among birds, particular domestic poultry, but it is relatively rare in humans. However, there are sporadic outbreaks in humans; since November 2003, there have been 608 confirmed cases in 15 countries – mostly in Asia – with a high (59%) mortality rate, according to the Centers for Disease Control and Prevention.
The vaccine was studied in two pivotal studies of 5,241 patients, including 3,574 who received the Q-Pan H5N1. In a phase III study comparing the vaccine with a saline placebo, seroconversion rates 42 days after the second dose were 90% among those aged 18-64 years and 74% of those over age 64 years. This exceeded FDA criteria for immunogenicity for a vaccine. Injection site reactions were the most common adverse reactions.
The vaccine is being considered for an accelerated approval, with the immune responses to the vaccine being considered a surrogate for clinical effectiveness. Moreover, the vaccine is manufactured using the same process as GSK’s seasonal influenza vaccine, FluLaval; full approval is dependent on postapproval studies confirming clinical benefit.
The Q-Pan H5N1 vaccine has been licensed in 30 countries, including in Europe and Australia, and is under review in Canada.
The FDA usually follows the recommendations of its advisory panels, which are not binding. Panelists have been cleared of potential conflicts of interest related to the topic of the meeting, although a panelist may be given a waiver. No waivers for conflict of interest were granted at this meeting.